Most seed drills in common use dispense the seeds in a dry state and it is known to be a requirement to dispense the seeds at a rate which is matched to the forward speed of the seed drill moving over the ground so that the seeds are distributed evenly. It is also known that there are advantages in sowing seeds in a wet state, especially after they have been allowed to imbibe water for a specified time and to become partially germinated. The main advantage is that the seed can be partially or completely germinated under determined conditions before drilling either into the field, into seed boxes or into soil blocks, with the result that the crop growth is quicker, more controlled, and has a greater reliability of a viable plant at each required position. It is known to dispense seeds in this wet state by suspending the seed in a flowable, semi-liquid gel, for example provided by carboxymethyl cellulose. One simple method of dispensing such a gel is to contain the gel in a bag with an aperture at one end and to squeeze the bag so as to express the gel as a narrow trail of material in much the same manner as sugar icing is applied to cakes as a decoration. It is also known, as disclosed in U.K. patent specification No. 1,045,732 (Elliott), to dispense seeds in a gel by a mechanism secured to a mobile frame for movement over the ground the frame carrying a pumping arrangement for squeezing out a trail of gel at a rate related to the movement of the land wheels of the frame.
In operation however a number of disadvantages have been found with both the above methods of dispensing seeds in a gel. In the case of a simple manual method described, the operator has the difficult task of matching the rate of delivery of the gel to the rate of movement of the aperture over the ground (or other material to which the gel is being applied). In the case of the automatic frame mounted dispenser, the equipment is complicated and expensive and unsuitable for adaption to manual small scale use, for use in confined circumstances such as a greenhouse, seed boxes or small planting area. Furthermore inaccuracies can arise if slippage occurs between the land wheels and the ground since the amount of material delivered is related to the rotation of the ground wheels.
There are also known, for example as described in U.S. Pat. Nos. 1,423,932 (Garner) and No. 2,390,969 (Traphagen), mobile seed drills, known as check row planters, which operate by securing at one or more fixed locations spaced apart across a field a line on which are mounted equally spaced buttons. The mobile seed drill is driven across the field beside the line and a sensor arm engages the line and senses the passage of each button. As each button passes, it catches on the arm and imparts a motion to the arm which releases one or more seeds to be planted in the ground. Such check row planters operate to plant dry seeds discontinuously in response to discrete movements imparted to the sensor arm by the buttons.
Finally, there are also known a number of devices for dispensing material in the form of a paste or semi-liquid by manual rotation of a drive rotor to drive an output means which expels material from a container. Such devices have been used previously for dispensing materials such as toothpaste, cake icing or ceiling compounds, and examples are found in U.K. Pat. Nos. 944,520 (Crudgington) and 955,346 (Bouet). Use of such a device gives rise to the same difficulties discussed above in relation to dispensing seeds in a gel from a squeeze bag, that is to say that the operator has to match the rate of delivery to the speed of movement over the working surface.